1. Technical Field
The present disclosure relates generally to the dynamic frequency control of a central processing unit (CPU), and more particularly to technology that selects optimum operating frequency using latency information in order to reduce the energy, consumption of a CPU.
2. Description of the Related Art
With the advancement of informationization, power consumption in the field of Information Technology (IT) has rapidly increased year after year. In order to reduce the power consumption of IT devices, technology for monitoring power consumption for each device in real time, technology for controlling power, technology for automatically shutting off standby power, etc. have been developed.
In particular, in order to reduce the power consumption of a CPU, i.e., a core component of IT devices, CPU Dynamic Voltage and Frequency Scaling (DVFS) technology that controls frequency and voltage that are applied to the CPU has emerged. Furthermore, CPUIdle technology that controls a CPU in an idle state, i.e., a state in which substantially no tasks are being performed, has been developed.
According to technology for actually controlling the operating frequency of a CPU using DVFS, a CPU is driven at maximum operating frequency when the application load of the CPU is high, and the CPU is driven at lower operating frequency when the application load of the CPU is low.
Furthermore, Linux is in charge of the selection of the operating frequency of a CPU, and provides a governor, i.e., a module that changes the operating frequency of a CPU, using the DVFS interface of a BSP. Accordingly, the administrator of a system can guarantee an optimum execution state by selecting a specific governor according to the situation of the system.
Furthermore, the CPU DVFS governors of Linux include maximum frequency performance (Performance) type governors, minimum frequency performance (Powersave) type governors, load-based operating frequency selection (Ondemand, Conservative) type governors, etc. So far, various governors for mobile platforms have been proposed.
In particular, it is known that an average load information-based DVFS governor that has been proposed to overcome the problem of tasks that are asymmetrically executed in individual cores of a multicore CPU system has relatively optimum power efficiency. However, an additional algorithm is required for the average load information-based DVFS governor to select operating frequency for a maximum reduction in energy consumption through more accurate prediction.
A CPUFreq framework predicts future operating frequency using the state information of a system during a predetermined time. Although a conventional CPUFreq framework sets operating frequency using the load information of a system, the CPUFreq framework needs to set operating frequency based on various types of information in order to select a more accurate operating frequency.
Furthermore, the conventional CPUFreq framework and a conventional scheduler cannot collect information about the performance state of each other, and the CPUFreq framework cannot obtain information about the influence that is exerted on the scheduler due to a change in operating frequency.
Therefore, there is an urgent need for technology that selects optimum frequency while taking into account information generated during the performance of a scheduler as a frequency selection factor of a CPU DVFS governor.
In connection with this, Korean Patent Application Publication No. 10-2015-0067869 published on Jun. 19, 2015 discloses a technology related to “Dynamic Power Control Method in Multicore Environment.”